BE1027329B1 - SOLID STATE COMPRESSOR - Google Patents

Abstract

The present invention relates to a solid state hydrogen compressor, comprising at least one membrane fixed between two porous electrodes, together forming a membrane-electrode assembly, a pair of cell plates or bipolar plates, between which the membrane assembly- electrodes is attached, wherein the membrane has a larger area than the porous electrodes and protrudes outside an area of the porous electrodes; and the cell plates have a larger area than the membrane and protrude outside an area of the membrane; two insulating gaskets each surrounding one of the porous electrodes; covering the part of the membrane which protrudes outside the region of the electrodes and protrudes outside the region of the membrane, further comprising a reinforcing layer, disposed between the insulating joints, on the outside of the electrode area.

Description

Solid State Compressor The present invention relates to a solid state compressor, in particular a solid state hydrogen compressor, and more particularly the sealing of such a compressor.

The heart of a solid state hydrogen compressor is a membrane which is normally fixed between two porous electrodes, together forming a membrane electrode assembly (MEA). The electrodes are porous to allow gases and fluids to pass to and from the membrane, and electrically conductive to allow current to be affected. The membrane-electrode assemblies are fixed between cell plates (also called bipolar plates) which are complex structures with multiple functions: they mechanically support the membrane-electrode assemblies, allow the passage of current, and feed and divert gases and gases. water to and from the membrane-electrode assembly. The combination of the membrane-electrode assembly and the bipolar plates or cell plates surrounding it is generally referred to as a cell. A solid state compressor is normally composed of several cells to obtain sufficient capacity (total membrane area). To be cost effective and to allow current to flow through the cells without wiring, the cells are stacked in series and secured between end flanges. This is well known in the art of fuel cell stacks, which are stacked in a similar manner and for the same purpose. Unlike fuel cell stacks which normally operate at a pressure of a few bars, in the case of a hydrogen compressor, the end flanges and cell plates must provide sufficient strength and stability to contain the gas. operating pressures of the compressed gas which can exceed 1000 bars.

In fuel cell stacks, the membrane-electrode assemblies are fixed between the bipolar plates and have a non-conductive edge (the rim / seal) that prevents current from passing directly from one electrode to another around it. membrane-electrode assembly (an electrical short circuit) and which often also provides a sealing mechanism at the same time. Sometimes the sealing function is performed by other parts such as gaskets. In the case of high pressure solid state compression stacking, the same insulation and sealing functions as for fuel cells must be performed. Both of these functions can be conveniently performed using an insulating polymer (film). The polymer (film) can either "wedge" the membrane of the membrane electrode assembly, or be used on one or both sides of the membrane and form an insulating "seal".

By exerting mechanical (vertical) pressure on this edge polymer, sealing can be achieved and mechanical pressure greater than the compressive pressure is applied. In some cases, this can be greater than 700 bars or 1000 bars. However, at these very high sealing pressures, the polymer and / or the polymer and the membrane can be plastically deformed and forced out either between the bipolar plates or in the orifices necessary for the passage of gases and / or liquids to the membrane-electrode assembly or the orifices for the cooling fluids.

… The extent of the deformation depends on the characteristics of the polymer materials and their thickness. The thicker the layers and the more plastically deformable they are, the easier it is for materials to "flow". In any sub-volume of a polymer, molecular chains have a certain degree of freedom to move or stretch. The thinner a polymer sheet, the less this flexibility allows the central portion of the polymer sheet to move / deform sideways.

Another way to ensure a sufficient seal with tolerable lateral deformation is to make the border very wide. This increases the ratio of the side portion of the polymer to its thickness, however, it increases the cost and size of the peripheral structures. The object of the present invention is to eliminate the drawbacks of solid state compressors of the state of the art, or at least to provide a useful alternative. The present invention thus provides a solid state hydrogen compressor, comprising at least one membrane fixed between two porous electrodes, together forming a membrane-electrode assembly, a pair of cell plates or bipolar plates, between which the membrane assembly -electrodes is fixed, wherein the membrane has a larger area than the porous electrodes and protrudes outside an area of the porous electrodes; and the cell plates have a larger area than the membrane and protrude outside an area of the membrane, two insulating gaskets, each surrounding one of the porous electrodes, covering the portion of the membrane that protrudes beyond the membrane. outside of the electrode region; and protruding outside the area of the membrane, and a reinforcing layer, disposed between the insulating gaskets, outside the area of the electrodes. The reinforcing layer can be a high pressure gasket, that is, a gasket capable of withstanding pressure up to 50-1000 bar, which allows to isolate and achieve edges of manageable size . The reinforcing layer may for example surround the membrane, and therefore be located at the point where the joints protrude from the surface of the membrane.

Preferably, the reinforcing layer fills the area between the insulating joints around the membrane. A uniform distribution of the forces exerted on the joint and the reinforcing layer is thus obtained.

The reinforcing layer can be made of an insulating material like Kevlar, which has the advantage of reducing the risk of electrical short circuit, but it can also be a metallic layer, which can be advantageous in because of its great resistance.

In general, the solid state hydrogen compressor according to the present invention can have a round cross section, the membrane, the electrodes and the cell plates all having round cross sections and the gaskets and the backing layer having cross sections. ring-shaped.

This leads to a sturdy construction.

The reinforcing layer may be in the region of the bipolar plates.

It can therefore be kept as small as necessary, without going beyond the stack forming the hydrogen compressor.

For optimum insulation, the seal can protrude from the membrane on either side of it in the direction away from the porous electrodes.

The gasket can be made from a polymer, which can be an ordinary polymer used in hydrogen compressors according to the state of the art, but the backing layer allows the gasket to be thinner, and therefore d 'have a lower risk of deformation.

Otherwise, it is also possible to apply several reinforcement pieces, in particular surrounding channels in the solid state hydrogen compressor.

These channels can be intended for the cooling liquid or for a gas to be compressed, such as hydrogen.

A reinforcing structure can also be integrated or embedded in the polymer edging material, most convenient being by rolling.

Preferably, here also a metallic reinforcement can be used, but other reinforcing materials such as Kevlar etc. can be used.

This reinforcing structure prevents outward deformation of the polymer by allowing thinner polymer layers which can withstand greater lateral shear force.

Ideally this structure is of a suitable thickness and in combination with the polymer film makes the border of a thickness in the same range as the membrane-electrode assembly itself so that flat bipolar plates can be used.

The thickness of the framework can be between 1 and 200 µm, while the thickness of the bipolar plates can be between 200 and 5000 µm.

Since the reinforcing structure is insulated between the polymer sheets, it can be of conductive material since the polymer provides the insulating characteristic, but an insulator can also be applied, and even be preferred.

Alternatively, for intermediate pressure systems, if the membrane itself is part of the rim, smaller reinforcement structures can be integrated or embedded around the smaller holes to prevent the membrane and / or polymer from deforming. in the orifices.

The invention will now be explained in more detail, with reference to the following figures, among which: FIG. 1 shows a fuel cell according to the state of the art; FIG. 2 shows a stack of fuel cells according to the state of the art; FIG. 3a shows a detail of a first embodiment of a stack of fuel cells according to the state of the art; FIG. 3b shows a detail of a second embodiment of a stack of fuel cells according to the state of the art; FIG. 4a shows a first detail of a problem associated with the state of the art; FIG. 4b shows a second detail of a problem associated with the state of the art; Figures 5a and 5b show details of the present invention.

FIG. 1 shows a fuel cell according to the state of the art.

The cell comprises a membrane 2, fixed between the electrodes 3, 4, formed by blocks of graphite.

Between the membrane and the respective electrodes, gas diffusion supports 7, 8 are present, with an area or area smaller than the surface of the membrane 2 and the electrodes 3, 4. The diffusion supports are surrounded by Teflon masks 5, 6. FIG. 2 shows a stack 10 of several fuel cells 1 according to the state of the art.

Stack 10 comprises several fuel cells 1 as shown in Figure 1, separated by cooling plates 11, 12, 13, 14. The fuel cells are fixed between end plates 15 and 16. Figure 3a shows a detail of a first embodiment of a fuel cell 1 of figure 1 in a stack of fuel cells, as shown in figure 2. In the figure, it is visible that the membrane 2 extends beyond the electrodes 7, 8. Where it extends, it is fixed between joints 5, 6. The joints are larger than the area on which the membrane 2 extends beyond the electrodes 7, 8 and engage each other outside the membrane surface. This is indicated by region A.

Figure 3b shows a detail of a second embodiment of a fuel cell 1 of Figure 1 in a stack 10 of fuel cells, as shown in Figure 2. In the figure, it is visible that the membrane 2 extends beyond the electrodes 7, 8. Where it extends, it is fixed between Teflon masks 5,

6. The joints are just as large as the area on which the membrane 2 extends past the electrodes 7, 8 and, in this embodiment, do not engage outside the surface of the membrane. This is indicated by region A.

Figure 4a shows a problem associated with the prior art fuel cell 1, in a fuel cell stack 10 as shown in Figure 3a, once mechanical sealing pressure is applied to it. The stack of cells 10. It can be seen in the region indicated by B that the seals 5 and 6 have moved in a direction perpendicular to the sealing pressure, each with a different magnitude. The region indicated by C shows the effect, the two masks are pressed out of stacking, also in a different magnitude.

Figure 4b shows a second detail of a problem associated with the state of the art, when the seals 5, 6 are located in the vicinity D of a through hole 10 of the cell plates 3, 4, for example for the liquid cooling or for hydrogen. The force to assemble the compressor pushes the seals 5, 6 into the through hole 10, which can then be unintentionally blocked or partially blocked.

Figure 5a shows a detail of the present invention. As can be seen in the figure, the membrane 2 extends outside the electrodes 7 and 8. Where the membrane extends outside the electrodes, gaskets 5 and 6 are placed between the electrodes. cell 3, 4 and membrane 2. Where the membrane stops, a reinforcement 9 is placed between the joints 5 and 6. The reinforcement 9 has a thickness comparable to that of the compressed membrane 2, while the joints 5 and 6 have thicknesses comparable to those of the electrodes. As a result, the seals remain in their intended locations.

Figure 5b shows a similar configuration, with a through hole at location E. Around the through hole a small reinforcement is applied, with a corresponding hole 10, to prevent the seals 5 and 6 from being pressed into the through hole. 10. In such a configuration, several reinforcements can be applied.

The examples given are given by way of example only and in no way limit the scope of the present invention, as defined in the following claims.

Claims (12)

Claims 1. Solid state hydrogen compressor, comprising: - at least one membrane fixed between two porous electrodes, together forming a membrane-electrode assembly; - a pair of cell plates or bipolar plates, between which the membrane-electrode assembly is fixed; wherein the membrane has a larger area than the porous electrodes and protrudes outside an area of the porous electrodes; and o the cell plates have a larger area than the membrane and protrude outside an area of the membrane; - two insulating gaskets, each one surrounding one of the porous electrodes; o covering the part of the membrane which protrudes outside the region of the electrodes; and o protruding outside the membrane surface; characterized by a reinforcing layer, arranged between the insulating joints, outside the area of the electrodes, in which the reinforcing layer has a thickness comparable to that of the attached membrane, and the joints have thicknesses comparable to those of the electrodes. 2. A solid state hydrogen compressor according to claim 1, wherein the reinforcing layer surrounds the membrane. 3. A solid state hydrogen compressor according to claim 1, wherein the backing layer fills the area between the seals around the membrane. 4. A solid state hydrogen compressor according to claim 1 or 2, wherein the reinforcing layer is a metal layer. 5. A solid state hydrogen compressor according to any preceding claim wherein the gasket is made of polymer. 6. A solid state hydrogen compressor according to any preceding claim, wherein the gasket is made of Kevlar. 7. A solid state hydrogen compressor according to any preceding claim having a round cross section, wherein the membrane, electrodes and cell plates have round cross sections and the gaskets and the backing layer have round cross sections. Ring-shaped cross sections. 8. A solid state hydrogen compressor according to claim 1, wherein the backing layer is within the region of the bipolar plates. 9. A solid state hydrogen compressor according to claim 1 or 2, wherein the seal extends beyond the membrane on both sides of the membrane in the direction opposite to the porous electrodes. 10. A solid state hydrogen compressor according to claim 1, comprising a plurality of reinforcing parts, surrounding channels in the solid state hydrogen compressor. 11. A solid state hydrogen compressor according to any one of the preceding claims, wherein the reinforcing layer is a high pressure seal, capable of withstanding a pressure of up to 1000 bar. 12. A solid state hydrogen compressor according to any preceding claim, wherein the reinforcing structure can be embedded in a polymeric edge material, in particular by rolling.